Most people recommend a maximum of two weeks, but I have held eggs 21+ days with excellent results. Why that long you ask? I originally had one of the old Sears round metal incubators. I'd hatch a 'bator full, disinfect, and start again with whatever eggs I had collected while the first lot incubated.

Eggs were stored in an earthen cellar, approximate temperature of 65 degrees, humidity of 50% or better and were turned daily while waiting for incubation. Also, very importantly they were not 'shipped' eggs. That's another whole story.